Topography of visually evoked brain activity during eye movements: lambda waves, saccadic suppression, and discrimination performance.

Eye movement-related brain activity was studied in 14 subjects by recording EEG topographically in 16 channels over the occipital brain areas. Potential fields obtained with or without the simultaneous presentation of a visual stimulus during the time course of horizontal saccades were compared. Without visual stimulation, eye movements were followed at a mean latency of about 65 ms by a lateralized occipital dominant component whose topography was determined by the direction of the saccade but whose latency was independent of the time course of the eye movements. This component was reminiscent of lambda waves, however, it could also be elicited in complete darkness. When stimuli were presented during saccades, component latencies increased significantly, and there were also topographic changes in the evoked potential fields. Negative centroids were located more anteriorly and positive ones more posteriorly on the scalp when compared to brain activity recorded with stable eye positions and visual stimulation. All subjects reported no suppression of visual stimuli when presented during saccades occurred. This was confirmed by testing the discrimination performance of an independent group of 27 subjects. Our data show that the execution of saccades elicits electrophysiological patterns of activation in the visual cortex even without visual input. The increase of component latency observed during saccades as well as topographical differences suggest that visual information is processed by different neuronal elements during saccadic eye movements.